Just so you know, you don't have to comply with the DMCA. It's more intimidation then anything else. He will not have the legal basis nor the legal power/money to take this to court. Second, his code was purely written in open source as distributed by sourcepawn scripting. If he wants to claim ownership, he can't use open source code. Any person can fork off his code and he can't do anything about it. If he wants to claim ownership of the plugin, he will have to convert it to closed source coding such as C ++. I would keep distributing this until either a DMCA has been served by official legal staff and/or a court order.

Definitely the SMAC is as important as the own SourceMod, so if you want to keep your server free of damn cheaters, hope everything is resolved, meanwhile i'll save a backup of the modules of SMAC here.... just hope the FBI does not come knock on my door!